Thermostat control circuit



. Aug. 14, 1945.

T. J. -LEHANE ETAL THERMOSTAT CONTROL Filed Aug. 9, 1943 CIRCUIT 1 3 Sheets-Sheet l V A98 14 19455 T. J. LEHAE `Er 11u.- 2,382,073

THERMOSTAT CONTROL CIRCUIT Filed Aug. 9, 1943'J :s sheets-sheet 2 3 Sheets-Sheet 3 Filed Aug. 9, 1943 T. J.' LEHANE ErAL THERMOSTAT CONTROL yGIRCUIT Aug. 14, 1945.

SNN.

EN mow m90 YW MKV. hmm.

Patented Aug. 14, 1945 UNITED STATES nPATENTOEFIcE I 2,382,073 THERMOSTAT CONTROL cmcUIT Timothy' J. Lehane aud Everett n. Burgess, Chicago, Ill., assignors to Vapor Car Heating Com-- pany, Inc., Chicago, Ill., a corporation of New York Application August 9, 1943, sei-isi No. 497,938

12 Claims.'

This invention relates to'certain new and useful improvements in a thermostatically controlled electric circuit.

A principal object of the invention is t provide a thermostatically controlled circuit in which a master thermostat and a. control thermostat each function, under pre-determined conditions, to adjust the position of the other by means of directl heat winding connections between the thermostats.

A further object is to provide a thermostativcally controlled lcircuit of the above character which is particularly suitable for eifecting modulated operation of means so controlling the heating of` a space that the temperature thereof will be maintained substantially constant.

For the purpose of this application, the term space is employed to designate any room, con- Y duit, container or other enclosure in which it may* be desirable lto maintain a predetermined tem- `perature.

The thermostats, in addition to being innuenced by the temperature of the space, are heated by auxiliary heat so as to anticipate the temperature of the space at which the thermostats are set to function. The invention also contemplates applying a large amount of auxiliary heat to the control thermostat so as to increase its sensitivity plication of heat to the other thermostat and in this way puts such thermostat in readiness to intercept or oppose a change in temperature before any substantial change is reflected in the actual temperature of this space being controlled.

A further and somewhat general Object of the invention includes the provision of a thermostatically controlled circuit in which a self-cycling thermostat is so connected in thev circuit that its self-cycling action is varied in relation to the condition of other elements in the circuit. Speciiically, this feature of the invention includes Y a provision of a control circuit in which a thermostat is so connected with a plurality o1' resistors adapted to be vcut inl and out of the thermoin the temperature of the controlled space or in operating changes of other elements in the circuit, so as to vary the amount of auxiliary heat applied to the thermostat, and consequently the 'stat circuit in response to changes taking place 55 rate or frequency of its cycling action.

A further object of the invention includes provisions whereby auxiliary heat. may be applied to both the master thermostat'and the control 'thermostat in a. desired manner to minimize any lag between the cooperative functions of these elements.

'In situations where the current used is of such intensity as to cause substantial sparking at thermostat contacts, the invention includes the provision of suitably arranged relays or other devices for preventing such sparking. y

Inasmuch as the invention may be, embodied in control circuitsy for use in many situations either directly or=indirect1yV associated with a controlled temperature, three specic embodiments are shown herein. -It should be understood, however, that the speciiic circuits `herein shown, as well as the control temperaturesv used,

are merely illustrative and are not intended as limitations on the scope of the invention or on the uses for which the control system isv adapted.

In the drawings, Fig. 1 illustrates diagrammatically a means for heating or cooling a space together with a control circuit for modulating4 the position of a damper for controlling the supply of heat delivered to the said space.

Fig. 2 is a diagrammatic representation of a mechanism for maintaining the temperature of a circulating fluid, for example, the oil of an engine crank case at a predetermined temperature.

Fig. 3 is a diagram of the control circuits employed in connection Awith the iiuid circulating` system shown in Fig. 2; and l Fig. 4 is a modiiied circuit for controlling a reversible motor similar to the embodiment shown in Fig. 1, but using only one thermostat.

Referring rst to Fig. 1 of the drawings, ill

designates a' conduit for directing air into a space whose temperature'is beingcontrolled. The conduit, for a portion of its length, is provided,with a partition Il Awhich divides it into twoepassages. A heating element I2 is positioned inione of the passages and a-cooling element I3 is positioned in the other. A damper I4 is located in the conduit to control the amount of heated or cooled 'l air entering the controlled space. In one extreme posltionfof the damper, for example a position Il, indicated in ldotted lines, only heated air can be'l introduced into the space. In the other extreme position I 4b, only cooled air can be in- 2 troduced into the space. However, whenever the damper is in any intermediate position, 'both heated and cooled air are admitted in proportion determined by the position of the damper. 'Ihe operation of the damper is modulated by means of a reversible motor I5 whose movements are controlled in relation to the temperature of the controlled space. If the said space is maintained at the desired temperature, ,the damper operating motor I5 will remain inactive. If there should be a slight change in the temperature of the space, the control motor I5 will be operated in the proper direction to effect a compensating adjustment of the damper so as to increase or reduce the supply of heat to the space as may be required to balance the control system.

One approved control circuit for modulating,

the position of motor I5 comprises a master thermostat I6, a control thermostat I'I, a, relay I8, a relay I9 and a plurality of cycle resistors 20, 2|, 22 and 23, and connectors for connecting the above elements in the manner hereinafter, described.

Both thermostats I6 and-I1 are of the mercurycolumn type and are arranged in the space being controlled so as to be influenced in their operation by the temperature of said space. The thermostats are manufactured to function at certain pre-determined temperatures. However, the thermostats may be caused to function at any desiredv lower temperature of a controlled space by applying auxiliary heat to the thermostats to compensate for the difference between the desired temperature of the space being controlled and the actual temperature, at the thermostat, which will cause the mercury columns of the thermostats to engage their contacts. The specinc functioning of the temperatures of the thermostats will be different for, different situations. This is also true of the temperature range between the contacts of the thermostats when they are constructed, as is the case of the control thermostat of the present invention,` to maintain a fixedv range between upper and lower contacts, between which the mercury column isma-intained when the control system is in balance, that is to say, a xed range in which the mercury column of the thermostat may oscillate without resulting in any change in operation of the control system. For the purpose of this application, the master thermostat is shown as having two contacts 24 and 25. The lower contact 24 is preferably Apositioned to' be normally engaged by the mercury columnon the thermostat during the entire operation of the system. The upper contact 25 is positioned to be engaged by the mercury column when the temperature at the thermostat reaches 80. nected with the cycle-resistors 20, 2I and 22 so that one or more of the circuits, in which said resistors are positioned, may function to apply predetermined amounts of auxiliary heat to the mostat heater 26, thermostat I6 will function at a room temperature of '76 plus said 4 added heat. For eachadditional resistor put in circuit with said heater 26, an additional 4 of heat will be added thereto.

An electric heater 26 is con- The control thermostat I'I is shown herein as having a heater coil 21 and three contacts 28, 29 and 3D. The lower contact may be placed at any suitable location so as to be engaged by the mercury column of the thermostat during the normal operation of the control system. The middle contact 29 is placed at a location to be engaged by the mercury column of the thermo` stat at any suitable temperature of the thermostat within its range of operation, for example at 280. The top contact 30 is positioned to function at a higher temperature, for example 300.

The present disclosure contemplates adding' 400 auxiliary heat to the control thermostat. l

It will be apparent, therefore, that if the'full amount of 400 of auxiliary heat-were added for an appreciable period of time, the mercury column would rise to a position corresponding to the room temperature .plus the 400 of heat or 176 above the upper contact 30. This assumed condition is never obtained, since engagement of the mercury column of the control thermostat with the upper contact 30 results in breaking the energizing circuits for the heater coils 26 and 21 of perature spacing `between the upper contact and'v the middle contact is only 20, and it is within this space that the mercury column is normally maintained when the control system is in vbalance. It will be observed, therefore, that the middle contact 29 of the thermostat functions at a room temperature of '76 plus 204 added heat.

The manner. in which the thermostats cycle,

that is to say, the manner in which the mercury columns of 'the thermostats engaged their upper contacts and then receded from said contacts, will be apparent from the description of the specific circuits which may be in control of the thermostats from time to time. Assuming that the control system is de-energized, that the damper I4 is in a position to deliver equal amounts of heated and cooled air to the controlled space, and that the temperature of the said controlled space is 2 below the desired temperature of 76, the manual closing of the switch A establishes a circuit through wire 3I'to energize the coil of relay I8. 'I'his energization of relay-I8 moves its armature 31 to a position to close an energizing circuit through one field of the motor I5 to cause the motor to rotate in a direction vto adjust the position of the damper I4 so as to supply more heat to said space. This circuit includes the negative line 32, armature 33 of the de-energized relay I9, wires 34, 35 and 36 through armature 31 of energized relay I8, thence through wire 38 and field 39 of the motor I5 to wire 40 leading to the positive line 4I. The operation of motor during the initial heat-up of the space will continue until the damper `I4 assumes its maximum heat delivery position. At this time the motor circuit will be broken automatically by opening of a limit switch 42. After the space is heated and the control system is more nearly in balance, the motor I5 will operate onlyA momendamper I4.

When the heat-on" circuit through the motor I6 is closed, there are nOrmllY three Parallel circuits available to supply electric current to the heater coil 26 of the master thermostat. One of these circuits leads from the' movable contact 31 of the energized relay I8, by wires 38 and 43', cycle resistor 20, wire 44, heater coil 26, and wires 45 and 46 to the positive line 4I.

A second parallel circuit leads from the armature 33 of de-energized relay I9 through wire 34, adjustable cycle resistor 2|, wire 44, heater coil 26, and wires 45 and 46 to the negative line 4I.

'I'he third of said parallel circuits leads from the armature 33 of de-energized relay I9, through wires 34, 35 and 36 to heater coil 21 of the control relay, and thence through'wire 41, resistor 23, wire 48, resistor 22, )wire 44, heater coil 26, and wires 45 and 46 to the negative line 4 I.

v 'I'he resistor 23 does not add any additional heat tothe heater coil 26, since its function is merely to determine the intensity of current passing through the heater coil 21 during the functioning of control thermostat I1. The said resistor 23, therefore, may be incorporated in the heater 21 at the time of its manufacture to provide the desired value or it may -be retained as a variable resistor as shown herein so that the eiectiveposition of contacts 29 and 3l) may be varied relative to the desired temperature of the controlled space. For example, if it should be desired to control the space at-a temperature of 78 instead of the 76 herein previously mentioned, the resistor 23 and also, if desirable, the resistor 2I may be adjusted to reduce theA amount of auxiliary heat to the thermostats and thereby maintain a higher temperature. in the space 'being controlled. This change in the temperature of the space can be obtained without altering the fixed temperature spacing between contacts 29 andV 30. It will also be observed in this connection that the single thermostat I1, together with relays I6 and I9, function to eiect modulated movements of the motor I5 in opposite directions, and can be included in a system Without the functions of the master thermostat. A modiiled circuit of this character is illustrated in Fig. 4 of the drawings and will be described hereinafter.

The passage of current through the heater coil l 21 to 'the heater 26 of the master thermostat adds some heat thereto, but this added heat is insuillcient, because of the higher intensity of heater 21, to cause it to function. It will be seen, however, that approximately 12 of heat can be added to the master thermostat I6 =by virtue of the three parallel circuits containing the cycle resistors 20, v2| and 22, respectively. Consequently, during the initial heat-up of'the system, the mercury column of the master thermostat is caused to move into engagement with its contact 26 in a relatively short period of time.

In view of the fact that approximately 12 is added to the thermostat I6, during the initial Aheat-up thereof, it will be apparent that the mercury column thereof will reach the upper column 26 before the temperature of the space being controlled has. been 'raised to the desired tem-I perature 01,76". The riseof the mercury colvuxnnin the master thermostat to engage the 'upper contact- 26 -there'orpermits the electric current ilowing through the heater 21 of the control thermosta't to pola directly froniwire 48 through wire 48. contact, mercury column oi' the master to contact. and4 thence through wire 46 to the positive line 4I.

'Ihis circuit removes the resistor 22 from the circuit of heater coil 26 and consequently permits sumcient cooling of the master thermostat to permit its mercury column to recede from its 5 engagement with said upper contact 25. 'I'herefore, the circuit closed through said upper contact 25 is only momentary. However, such closing of a circuit through said contact establishes a momentary 400 heating circuit through the l heater coil 21 of control thermostat I1. As soon as the circuit through said contact 25 is lbroken lby the cooling of the thermostat I6 and consequent recession of its mercury column, the resistor 22 isagain made effective to add heat to the heater Vcoil so as to again cause the mercury to engage the contact 25 and thereby establish another momentary 400 heating circuit through the heater coil 21V of the control thermostat. This cycling action will continue until the auxilof the control thermostat are sufficiently frequent to cause the mercury column thereof to engage the 280 contact 29.

When the mercur scolumn of the said control thermostat engages e said middle contact 29, a circuit is closed from the negative line 32, through wire 50, contact 28, mercury column of fthe control thermostat, middle contact 29,

and wire 5| to a point in the relay energizing Y cycling of the master described.

It will =be noted from the above descriptionv that during the time the mercury column of contact 29, all cycling action of the master thermostat I6 is for the purpose of adjusting thecon- Lftrol thermostat by applying heat impulses thereto to raiseA its mercury column into engagement with themiddle contact 29. In effect, the master thermostat informs the control thermostat that a change of temperature in the space can be expected and endeavors to so adjustV or condition the control thermostat as to intercept and oppose the change in temperature by opening the heat on circuit through motor-I5. 'I'his cycling action, and consequently the said adjustment of the control thermostat I1 will continue until the temperature of the space being controlled rises to a point near the desired temperature of 76. At this time the cycling of masterrthermostat will 'be more frequent and therefore increases the frequency of impulses through heater 4 21 of control thermostat until its mercury col- -umn engages its upper contact 30. However, if conditions should develop, during the said adjustment of the control thermostat, to cause its mercury column to drop below the middle contact 29, the relay I8 will again'be energized `so that its armature will@ move to aj position to reclose the heater circuit containing the cycle re- Usistor 20 so as to add more heat to the master thermostat I6 and thereby adjust its mercury column toward its upper contact 26.

As soon as the' mercury` column ot the control lary heat impulses supplied to the heater coil 21 added and removed from the circuit during the thermostat as previously trol thermostat I1 remains below the middle coripose of illustrating rality of thermostats.

thermostat I1 engages the 300 contact 30, a circuit is established through wire 52, coil of relay I9 and wire 53 to the positive line. This circuit energizes relay I9 so as to move its armature 33 to a position to close a reverse, or heat cfr circuit through motor I5 as follows: negative line 32, armature 33 of energized relay I9, wire 54, limit switch 55, "heat off eld 56 of the motor .I5 thence through the motor armature and wire 40 to the positive line 4I. This motor circuit energizes the motor so as to move the damper I4 in direction to reduce the amount of heat. In addition to closing the last mentioned motor energizing circuit, the energization of relay I9 breaks all circuits then eiective to apply heat to heater coils of both thermostats. This results in a sudden recession of the mercurycolumns of both thermostats from their upper contacts. Such recession results in again deenergizing the relay I9 so as to re-establish lthe heater circuits containing cycle resistors 2| and 22 for the master thermostat. When this is done, the mercury column of the master thermostat is again moved into engagement with its upper contact 25 and heat impulse is thereby again passed through the heater coil 21 of the-control thermostat to again raise its mercury column toward the 300 contact 30. If said column actually engages the contact 30, there will be another energizing impulse established through the relay I9 so as to again close the circuit through the "heat off" field of the motor I5 and thereby impart another adjusting movement to the damper I4 in a. direction to reduce the amount of heat and', increase the amount of cooled air delivered to the space. This momentary making and breaking of the circuit through the motor I5..will continue until the system comes into substantial balance, at which time the mercury column of the master thermostat will be maintained at a height slightly below the upper contact. 25, and the mercury column of the control thermostat I1 will be maintained at a location between the contacts 29 and 30.

From the above, it will be seen that the master thermostat IB functions to adjust the height of the mercury column in the control thermostat I1, when the said mercury column is below the contact 30. However, `as soon as the mercury column of the control thermostat engages the' said upper contact 30, and also when the said mercury vcolumn drops below the contact 29, the said control thermostat functions to adjust the position of the mercury columnl of ,the'master thermostat. By the mutual adjustments of the thermostats, the control system is quickly moved to a position of substantial balance, and if there are any conditions encountered which cause the mercurycolumn of the control thermostat to drop below the middle contact 29, the heater circuits containingcycle resistors 20, 2I and 22 are again closed so as to re-establish a balanced condi- A tion. A

Referring now'to the-embodiment illustrated in Figs. 2 and 3"of the drawing'szln this modified embodiment the control system is employed in a situation in which it is desirable maintan a nuid, for example, the oil in an engine crank l, case at a substantially constant temperature. This specific installation is used merely for purthe control principle whereby a substantially constant temperature may be maintained in' situations requiring or using electric heater currents of Itwill be obvious, therehigh intensity for a plufore, that the principle can be applied to installacoil 58 and is returned to the crank case by means x of pipe 59, pump 60, and pipe 6I. The coil 58 is enclosed in a casing 62, through which drafts of air are intended to be passed either by means of a motor operated fan 63 or by the forward movement of the cooling system itself. The ow'of air through the casing 62 is controlled by means of a damper 64, whose position is controlled by means of a reversible motor 55 substantially as disclosed in the previously described embodiment. In other words, the damper 63 is positioned by the operation of a motor to increase or diminish the flow of air through the casing 62. It will be understood that when the supply of air is diminished, the natural operation' of the engine will vincrease the temperature of the oil passing through the cooling system. In order to maintain the circulating oil at a pre-determined and substantially constant temperature; a master thermostat designated 96 and a control thermostat designated 61 are both inserted in the conduit 59 so as' to be influenced by the temperature of the circulating oil. In this respect, the conduit 59 and the oil therein can be regarded as the space referred to in connection with the previous embodiment. However, inasmuch as the "space in the present modification is maintained at a substantially higher temperature than the space Acontemplated in the previous embodiment, a modified control system is provided principally to apply auxiliary heat tdthe control thermostat 61 simultaneously vwith the application of maximum heat to the master thermostat 65. Inasmuch as the modied embodiment of the inventionv includes the use of heater currents of greater intensity on the master thermostat, a re- In the modified installation the master thermostat 65 is provided with two contacts 59 and 69. The lower contact may be positioned at anylocation so as to be engagedl by the mercury column during the entire operation of the control system. The upper contact 68, for the purpose of the present disclosure, is located to be closed when the temperature at the thermostat reaches that is to say, the normal operating temperature of the oil in duct 59 of approximately l00 plus 90 of added heat. However, the actual amount of added heat to the thermostat 65 maybe as high'as desired. For

'the present consideration it may be assumed that the total of 200 of heatmay be added to the thermostat by means of its heater coil 10 in conjunction. with the several resistors inl circuit therewith as will be hereinafter described. The addition of 200 of auxiliary heat to the thermostat' 56 insures-quick adjustment of its mercury columnnto bring about engagement with the upper conta'ct 58 so as to bring about the desired cyclinl'g 'action of the thermostat. The cycling action is produced by the making and breaking of an electric circuit at the contact 58 and thereby varying the intensity of electric current supplied to the heater coil 10.

assao'ra The control thermostat is provided with three contacts 1|, 12 and 13. The lower contact 1| may be located in any suitable position so as to be engaged by the mercury column during the entire operating period of the control system.

. The middle contact 12 is located to be engaged by the mercury column when, the temperature at the thermostat rises to 280, that is to say, the normal temperature of the oil of 100 plus 1807 of auxiliary heat. The upper contact 13 is positioned to close when the temperature at the thermostat reaches 300. It may be assumed that 400 of auxiliary heat may be added to the control thermostat by means of its heater coil 14 in conjunction with the cycle resistors, hereinafter mentioned, which are in circuit with said coil. It will beobserved that the addition of 200 of auxiliary heat to the master thermostat 66 and the addition of 400" of auxiliary heat to the control thermostat 61, together with arrangement of their upper contacts substantially below the maximum theoretical range of the thermostat, make the control system highly sensitive to any change in the temperature of the oil in conduit 59.

The operation of the modied system is much the same as described in connection with the previous `embodiments except that the modified system includes the operation of an additional relay and an arrangement of means whereby the heater coils of the master thermostat 66 and the control thermostat 61 may be heated simultaneously during certain periods of operation of the system. The modified embodiment also involves applying a greater amount of auxiliary heat to the master thermostat than was described in connection with the embodiment shown in Fig. 1.

The operating parts of the modied system may be briefly described as including the master and control thermostats 66 and 61, respectively1 togetl'rer with their heater coils 10 and 14, respectively, resistors 15, 16 and 11 for controlling the intensity of electric current to the coil 10, resistors 18 and 19 for controlling the intensity of electric current to the heater coil 14, relays 80, 8| and the additional relay 82, and the motor 65.

Assuming that the system is de-energized throughout, it is set into operation by the manual closing of a switch B in the negative line 83 to close an electric circuit through the coil of relay 80 and also circuits through the heater coils and 14. The energizing circuit through the coil 80 includes the negative line 83, Wire 84, resistor 85, wire 86, coil of the relay 80, and wire 81 to the positive line 89. The energization of relay 80 moves its armature 90 to a position to close an energizing circuit through one field of motor whereby the motor is operated in a direction to adjust the damper 84 to reduceithe Ilow of cooling air across the coil 58, and thereby permit the temperature of the oil therein to rise to the desired operating temperature. The said motor energizing circuit is as follows: negative linc 83, wire 9|, armature 92 of de-,energized relay 8|, wires 93 and 94, armature 90, energized relay 80, wires 95 and 96 through the heat on eld 91 of the motor 65, thence through Wire 98 to the negative line 89. When the said relay 80 is energized, .there are established three possible parallel paths for the flow of electric current to the heater coil 10 of the master thermostat. One of said parallel paths leads from the relay 90 of the energized relay 80 through wire 95, cycleresistor 15, wire 96 and wire 91 through cycle resistor 16, wire 98, heater coil 10 and wire 99 to the positive line 89. The second, but most direct path, leads from armature 92 of de-energized relay 8|, wires 93, 94 and |00, relay armature |0| of de-energized relay 82, thence through wire 96, cycle resistor 16, wire 98, coil 16, and wire 99 to the positive line 89.

The third circuit path leads from armature 92 of de-energized relay 8|, through wires 93 and 94, variable cycle resistor 11, Wire 91, cycle resistor 16, wire 98, coil 10, and wire 99 to the positive line 89. During theI initial heat-up of the system, and at all other times when the relay 82 is de-energized, the second circuit path above described, including the single resistor 16, is in control of the heater coil 10. However, when the relay 82- is energized, the circuit through the heater coil 10 is altered so that the resistor 15 is connected in series with resistor 16 through the said heater coil 10, so as to substantially reduce the intensity of the electric current supplied to the heater 10. Thev third circuit path is also effective when the relay 82 is energized to direct additional current through the variable resistor 11 which is connected in series with the resistor 16.

Simultaneously with the establishment of heatup circuits for the master thermostat coil 10. a heat-up circuit is established through the heater coil 14 of control thermostat 61. This heat-up circuit leads from the armature 90 of energized relay through wires 95 and |02, through variable resistor 19, wires |03 and |04, heater coil 14 and wire |05 to the positive line 89. The windings of resistor 19 in conjunction with the heater coil 14 are such as to apply approximately 200 of auxiliary heat to the control thermostat 61. It will be seen, therefore, that during the initial heat-up of the system the auxiliary heat applied to the master thermostat and the control thermostat is approximately equal.

'Ihe heat-up of the thermostats 66 and 61 will continue at the above rate until the mercury column of the master thermostat 66 engages the 190 contact 6,8. When the mercury column of thermostat 61 engages its said upper contact 68, the relay 82 is energized by a circuit leading from armature 92 of deenerglzed relay 8| through wires 93, 94 and |06 to the coil of said relay 82, thence through wire |01, contact 69, mercury column of thermostat 66, contact 68, and wires |08 and 99 to the positive line 89. The energization of the said relay 82, as previously indicated, opens the direct heater circuit through coil 10 and permits the introduction of two additional resistors 15 and 11 to be introduced in series with the resistor 16, and therefore reduces the heating effect on the coil 10 so as to cause the mercury column to recede from the contact 68 of the master thermostat. 'Ihe closing of said relay 82 also establishes an additional 4circuit through the heater coil 14 of the control thermostat 61 so as to apply more auxiliary heat to the said control thermostat; This heater circuit leads from armature I0|,of energized relay 82, through wire |09, resistor 18, wire |04, heater coil 14, and wire |05 to the positive line 89. This additional heating circuit through the heater coil 14 is established only momentarily because of the fact that the cooling effect on the master thermostat 66, because of the reduced intensity of electric current through its coil 10, causes the mercury column of master thermostat 66 to recede from its contact 68, and therefore again cle-energize relay 82. This cycling action of the master thermostat 66 applies impulses of additional heat to the control thermostat 61 until the temperature at the control thermostat reaches 280 so as to cause its mercury column to engage the middle contact 12. The engagement of the mercury column with the said contact 12 closes a circuit which by-passes the electric current around the coil of relay 80 so as to de-energize this relay. The by-pass circuit is as follows: negative line 83, wire 84, resistor 85, wires 86 and I ID to the middle contact 12 of control thermostat, thence through the mercury column to contact 1| and lwire I I| to the positive line 89. If the temperature of the oil in conduit 59 has risen to a point near its normal temperature of 180, the mercury column or control thermostat will remain in the space between contacts 12 and 13 thereof. However, if the temperature of the oil in conduit 59 is substantially below the normal temperature desired, the opening of the circuit at the armature 90 of relay 80 removes the heater circuit including the resistor 19 from the heater circuit of the control thermostat. vThe mercury column of the thermostat will, therefore, recede from the middle contact and again eiTect re-energization of the relay 80 so asto re-establish the heater circuitV of full intensity for the coil 14. The thermostats 66 and 61 will cycle in the above manner until the temperature of the oil in conduit 59 plus the auxiliary heat applied to master thermostat 66 and control thermostat 61 is suflicient to maintain the mercury column of the mastervthermostat at a position near its contact 68. and to maintain the mercury column of control thermostat within the temperature range deiined by the contact 12 and the contact 13. The position of the mercury column of master thermostat 66, being maintained in close relation to the contact 68, increases the frequency of its cycling action and consequently increases the frequency of the heat impulses applied to the control thermostat 51. When the system is in substantial balance so as to maintain the oil at a substantially constant temperature, the frequency of the cycling action of the master thermostat 66 will be suicient together with the temperature of the oil to maintain the mercury column of control thermostat 61 within the temperature range of 20 as dened by the contacts 'I2 and 13. However, if the temperature of the oil should increase slightly above the normal temperature desired, this increase in temperature will be sufficient to raise the mercury columnvof control thermostat up to the upper limits of said temperature range so as to engage the upper contact 13 of the thermostat. When this condition takesl place, an energizing circuit is established through the coil of relay'l as follows: from negative line 83, through lthe coil of relay 8|, thence through wire ||2 to contact 13 of control thermostat, thence through the mercury column to the lower contact 1 I, and thence through Wire III to the positive line 89. The energization of relay 8| in the above manner closes an energizing circuit through the motor 65 to operate the motor in the reverse direction so as to impart through the chain belt I|3 an adjusting movement to the damper 64 to Aincrease the flow of cooling air through the casing 62 so as to elect a cooling action on the oil. This motor energizing circuit includes negative line 83, armature 92 of energized relay 8|, wire II4, heat off eld I|5 of motor 65, thence through the motor armature and wire 98 to the positive line 89. 'I'he energization of relay 8| will -be only momentary because the energization of relay 8| also functions to open all circuits, then available, for directing current to the heater coils 10 and 14 of both thermostats. The cooling effect on both thermostats will result in an abrupt recession of the mercury columns of said thermostats from their upper contacts and thereby break the last mentioned motor energizing circuit. However, the damper 64 will remain in its said adjusted position so that the cooling eiect on the oil will continue. However, if this cooling eiect is insuflicient to prevent the mercury column of control thermostat 61 from again reaching the upper contact 13, the re-engagement of thecolumn with said upper contact will again re-energize the heat off circuit of the motor 65 so as to impart a further adjustment to valve 64 to permit a greater volume of air to pass through casing 62. These adjustments will continue until the heat transfer is such that the control system will remain in balance with the mercury column of the control thermostat oscillating in the temperature range defined by contacts 12 and 13 without effecting engagement with either of said contacts.

It will be seen from the. description of the modied embodiment that the thermostats 66 and 61 function to adjust each other under pre-determinedconditions in substantially the same manner as that disclosed in connection with the embodiment in Fig. 1. It would also be apparent that the system, as herein shown or as modified to vary the amount of auxiliary heat applied to the respective thermostats, may be employed in various situations where i't is desirable to maintain a space at a relatively high but substantially constant temperature.

In Fig. 4 is illustrated a modified embodiment employed in a situation such as illustrated in Fig. 1 to maintain a uniform temperature of a space. This embodiment, however, employs only one thermostat, to wit, a control thermostat for controlling the operation of the reversible motor which in turn controls the supply of heated or cooled air to the space.

The mechanism for supplying the heated or cool air 'to the space of the present embodiment is preferably identical with the illustration in Fig. `1 and includes a conduit I0 having a partition II so as to divide the conduit into two passages, in

vone passage is arranged a heating element I2,

the reference numeral I4. In one extreme-position of the damper, for example position 4a indicated in dotted lines, only heated air can be introduced into the space. In the other extreme position I4b only cooled air can be introduced into the space. However, when the damper is in any intermediate position, both heated and cooled air are admitted in. proportion, determined bythe position of the damper. The operation of the damper is modulated by means of a reversible motor designated |5 whose movements are controlled in relation to the temperature of the controlled space. If the said space is maintained at a desired temperature, the damper operated motor I5c will remain inactive. If there should be a slight change inthe temperature of the space, the control motor I5c will be operated in the proper direction to effect a compensating adjustment of the ,damper so as to increase or reduce the supply of heat to the space as may be required to balance the control of the system. The system illustrated in Fig. 4 includes certain of the control elements indicated in Fig. 1, but are here designated by the same reference numeral with the addition of the exponent c, to wit, the control thermostat is designated 11 and corresponds to the control thermostat 11 of Fig. 1. The relays 18 and 19 correspond, respectively, to the relays" 18 and 19 of Fig. 1 and the motor 15 together with its iields 39, `58 and the limit switches 42 and 55 may be, and preferably are, the same as illustrated in Fig. 1 Assuming that the space being heated is to bemaintained at a temperature of '76 and that the actual temperature is substantially below 76, the manual closing of the switch A will establish an energizing current through the negative line 32, the amature 33 of the de-energized relay 19, wire 34, adjustable resistor 23, wire 41, heater 21 and wire 48 to the negative line 41. The resistor 23 is preferably adjustable so that any desired amount of temperature can be applied to theauxiliary heater 21 of the thermostat. Preferably the said resister 23 is so adjusted so as to apply approximately 400 of heat to the said auxiliary heater. Simultaneously with the establishing of the above circuit through heater 21 an energizing circuit is established through one side of the reversible motor 15 as follows: from the armature 33 of de-energized relay 19, wire 34, wire 36, armature 31 of de-energized relay 18, wire 38, limit switch 42, and eld 39 of motor 15, and thence -through wire 40 to the negative line 41. In view of the fact that the temperature of the room is substantially below the desired temperature of 76, the last mentioned circuit will result in moving the damper 14 to the position 14l whereby the maximum amount o f heated air will be supplied to the space. By the movement of saidmotor 15 to its limit in one direction, the limit switch 42 will be opened. Therefore, the maximum amount of heat will be supplied to the space until the temperature thereof is raised to approximately 76. The motor and damper will remain in their extreme heat on position so as to supply the maximum amount of heated air to the space being controlled. When the relay 18 is de-energized so as to close one circuit through the motor 15, it also establishes a circuit for supplying additional heat to the auxiliary heater 21 of the thermostat.

This circuit includes wire 111i, cycle resistor 111, wire 118 to wire 41, and thence through the heater 21 and wire 48 to the negative line .41. The resistor 111 may be designed to supply any desired amount of electric current to the auxiliary heater 21 of the thermostat which is less than the current supplied through the resistor 23. Preferably, the current supplied by resistor 111 is relatively small, for example current suilicient to add 4 of heat to the auxiliary heater 21.

After the motor 15 has been moved to its extreme heat-on position, nothing will happen until the mercury column of thermostat 11 engages the contact 29. At this point the circuit will be established through the relay 18 to break the motor circuit at that point. However, there is no change made in so far as the temperature of the room is concerned, until the mercury column engages the upper contact 30. At this time a circuit is established through negative line 32, branch mercury column of the thermostat, contact 30, wire 52, through the energizing coil of relay 19, and thence through wire 53 to the negative line 41.

19 so as to draw its armature 33 against the con- This circuit energizes the relay application of heat to the space.

tact to close an energizing circuit through the heat-olf iield of motor 15, thereby imparting an adjusting movement to the damper 14 in a direction to admit a quantity of cooled air into the space being controlled. This motor energizing circuit includes the negative line 32, the armature 33 of the energized relay 19, wire 54, limit switch motor ,leld 56, armature of motor 15, and

thence through wire 40 to the negative line 41. This motor energizing circuit will be only momentary, since the energization of the relay 19 breaks the circuit through the auxiliary heater 21 at the relay armature 33. Consequently, the mercury column will recede from the contact 30 and. therefore, deenergize the relay 19, thereby reestablishing the heating circuit through the auxiliary heater 21 so as to cause the mercury column to again rise into engagement with the upper contact 30 of the thermostat. will continue until a series of momentary operations of motor 15 adjust the damper 14 so as to supply sufficient cooled air to the space to maintain the temperature of the space near the point desired and thereby maintain the mercury column of the thermostat at a location intermediate the contacts 29 and 30. If there should be a sudlden drop in temperature of the space suilicient to carry the mercury column below the contact 29 `of the thermostat, the relay 18 will be de-ener gized, so as to establish a reversing circuit through the motor 15 for the purpose of increasing the When the said mercury column dropsl below the contact 29, the resistor 1 11 is made effective, by the de-energization of relayA 18, to supply additional current to the auxiliary heater 21 so that this additional current in conjunction with the current passing through the resistor 23 will quickly raise the temperature at the thermostat to a position above the contact 29.

The resistor 23 is made adjustable and'corresponds to the resistor 23 of the embodiment shown in Fig. 1 so that the temperature band as defined by the space between contacts 29 and 30 may be raised or lowered by varying the resistance and thereby raise or lower the point at which the temperature of the space is to be controlled.

We claim:

1. In a temperature control system, movable mechanism adapted to be adjustably positioned to raise or lower the temperature of a space, means including a mercury column thermostat operable at lower and upper limits of a xed temperature range' to energize said movable mechanism to effect adjusting movements thereof, an auxiliary electric heater for said thermostat, and means for varying the intensity of electric current through said heater to vary the effective position of said ilxed temperature range at the thermostat relative to the temperature of the space being controlled.

2,'In a temperature control system, movable mechanism adapted to be adjustably positioned to raise or lower the temperature of a space, means including a thermostat operable at lower and upper limits of a fixed temperature range at the thermostat to energize said movable mechanism to effect adjusting movements thereof, an auxiliary heater for said thermostat, means including a second thermostat responsive to temperature changes and functioning at a pre-determined temperature at the thermostat to close an energizing circuit through said electric heater to adjust said first mentioned thermostat to a functioning position within said temperature range, an auxiliary This cycling action electric heater for said second thermostat and a plurality of energizing circuits for the last mentioned heater, one of said circuits being made ineffective'by the functions of said second thermostat.

3. In a temperature control system, movable mechanism adapted to be adjustably positioned to raise or lower the temperature of a space, means including a thermostat operable at lower and upper limits of a fixed temperature range at the thermostat to energize said movable mechanism to effect adjusting movements thereof, an auxiliary heater for said thermostat, means including a second thermostat responsive -to temperature changes and function-v ing at a lpre-determined temperature at the thermostat to close an energizing circuit through said electric heater to adjust said first mentioned thermostat at a functioning position within said temperature range, an auxiliary electric heater for said second thermostat, a plurality of energizing circuits for the last mentioned heater, one of said circuits being made ineffective by the functions of said second thermostat, and means controlled by the functioning of the first mentioned thermostat for controlling the energization of another of said parallel circuits vthrough said heater of the second thermostat.

` 4. In a temperature control system, movable mechanism adapted to be adjustably positioned to raise or lower the temperature of a space, means including a thermostat operable at lower and upper limits of a fixed temperature range at the thermostat to energize said movable mechanism to effect adjusting movements thereof, an auxiliary heater for said thermostat,

means including a second thermostat responallel circuits through the heater of the second` thermostat.

5. In a temperature control system, movable mechanism adapted to bey adjustably positioned to raise or lower the temperature of a space, means including a control thermostat operable at lower and upper limits of a fixed temperature range at the thermostat to energize said movable mechanism to effect adjusting movements thereof, an auxiliary heater for the control thermostat, a master thermostat for lcontrolling the supply of electric current to the auxiliary heater of said control thermostat, an auxiliary heater for the master thermostat, and means controlled by the functioning of the control thermostat at the upper limit of said temperature range for de-energizing the heater circuits for both thermostats.

6. In a temperature control system, movable mechanism including a reversible electric motor, a relay for closing an energizing circuit through the motor to adjust its position in one direction, a second relay for closing a circuit through the motor to adjust its position in the opposite direction, a control thermostat adapted to function at the lower and upper limits ofy a temperature range at the thermostat to control the said relays, an auxiliary electric heater for the control thermostat, and means for adjusting the control thermostat to a position within said temperature range including a master thermostat responsive to the temperature of said "space, an auxiliary electric heater for the master thermostat whereby it is caused to function at a temperature higher than that of said space, and means effective when the control thermostat moves below said temperature range to apply electric energy to the heater of said master thermostat.

7. In a temperature control system, movable mechanism including a reversible electric motor, a relay for closing an energizing circuit through the motor to adjust its position in one direction, a second relay for closing a circuit through the motor to adjust its position in' the opposite direction, a. control thermostat adapted to function at. the lower and upper limits of a temperature range at the thermostat to control vthe said relays, an auxiliary electricheater for the control thermostat, and means for adjusting the control thermostat to a position within said temperature rangev including a master thermostat, an auxiliary electric heater for the master thermostat, means for varying the intensity of electric current to the heater when the control thermostat is operating within he said temperature range, and means actuated by movement of the control thermostat to a position below said temperature range to supply additional electric current to the heater of said master thermostat.

8. In a temperature control system, movable mechanism including a reversible electric motor, a relay for closing an energizing circuit through the motor to adjust its position in one direction,

a second relay for closing a circuit through theA motor to adjust its position in the opposite direction, a control thermostat adapted to function at the lower and upper limits of a temperature range at the thermostat to control the said relays, an auxiliary electric heater for the control thermostat, and means for adjusting the control thermostat to a position within said temperature range including a master thermostat, an auxiliary electric heater for the master thermostat, means for varying the intensity of electric current to the heater when the control thermostat is operating within the said temperature range, means actuated by movement of the control thermostat to a position below said temperature range to supply additional electric current to the heater of said master thermostat, and means actuated by Ithe functioning of the control thermostat at the upper limit of said temperature range to deenergize the auxiliary heaters of both thermostats.

9. In a temperature control system, vmovable mechanism including a reversible electric motor. a relay for closing an energizing circuit through the motor to adjust its position in one direction, a second relay for closing a circuit through the motor to adjust its position in the opposite direction, and means for controlling the energization of said relays comprising a. pair of mutually adjustable thermostats of the mercury column type adapted to function at different temperatures at the thermostats for effecting the mutual adjustments thereof.

10. In a temperature control system, movable mechanism adapted to be adjustably positioned in opposite directions to vary the rate of heat transfer to or from a space, and means including a pair of thermostats for controlling the movements of said mechanism; each thermostat being provided with an auxiliary heater, and electrically energized means controlled by the functioning of each thermostat adaptedto make or break electric circuits lthrough the auxiliary heater of the other thermostat.

`11. In a temperature control system, movable mechanism adapted to be adjustably positioned in opposite directions -to vary the rate of heat .transfer to or from a space', and means including a' pairof mutually adjustable thermostats for controlling the movements of said mechanism, auxiliary electric heaters for each thermostat, means for simultaneously applying energizing current to said heaters, and means actuated by the funcfer to or from a tioning of one thermostat for altering the intensity of electric current supplied to the other thermostat.

12. In a temperature control system, movable mechanism adapted to be adjustably positioned in opposite directionsto vary the rate of heat transspace, means including a' pair of mutually adjustable thermostats for controlling the movements of said mechanism, auxiliary heaters for each of the thermostats, means for simultaneously applying energizing current to said heaters, and means actuated by the functioning of each thermostat for altering the intensity of the electric. current supplied to the heater of the other thermostat.

TMOTHY J.

LEHANE. EVERETT H. BURGESS. 

